import java.util.Scanner;

/**
 * @author lijunhao
 * 2023/7/11 zuoye
 * @description TODO
 */
public class Grade {public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("请输入考生成绩");
    int i = sc.nextInt();
    switch (i/10){
        case 10:
            System.out.println("A");  break;
        case 9:
            System.out.println("A");  break;
        case 8:
            System.out.println("B");  break;
        case 7:
            System.out.println("C");  break;
        case 6:
            System.out.println("D");  break;
        default:
            System.out.println("不合格");
    }
}
}
